Giving him knowledge about Bitcoin is also the same as directing him to a better place even though the final decision is in the hands of his friend. And since no one is held accountable when a friend loses on an investment, this is where every piece of good advice is needed before making a hasty decision. Because a wise enough decision will provide a few steps that might be better for people who are trying to invest in their life.
Only his friend alone can be blamed for the misfortune and the result of his decision. I've got those types of friends before that they've asked me what is bitcoin, stuff about it, and if it's a good investment and I'd told them everything and with a yes. But then later, it seems that they don't believe me and went to invest in altcoins, they just revealed that to me when they lost almost all of their capital to a shitcoin because they thought that I was wrong and they better. Remember that these people are just new to the market, they think that they're better than with those experiences and that's why they gather info and decide to follow their own decisions and not the good advises.
This is the reason on why i dont like on recommending or advising something when it comes to things not only on Bitcoin but also on other stuffs as well as i dont like on getting blamed when things goes shit and wrong.